Android Programing

1. Tutorial: Setup for
Android Development
Adam C. Champion
CSE 5236: Mobile Application Development
Autumn 2014
Based on material from C. Horstmann [1], J. Bloch [2], C. Collins et al. [4],
M.L. Sichitiu (NCSU), V. Janjic (Imperial College London), CSE 2221 (OSU), and other sources
1

2. Outline
• Getting Started
• Android Programming
2

3. Getting Started (1)
• Need to install Java Development Kit (JDK) to write
Java (and Android) programs
– Do not install Java Runtime Environment (JRE);
JDK and JRE are different!
• Can download the JDK for your OS at http://java.oracle.com
• Alternatively, for OS X, Linux:
– OS X:
• Open /Applications/Utilities/Terminal.app
• Type javac at command line
• Install Java when prompt appears
– Linux:
• Type sudo
apt–get
install
default–jdk at command line
(Debian, Ubuntu)
• Other distributions: consult distribution’s documentation
3

4. Install!
4

5. Getting Started (2)
• After installing JDK, download Android SDK
from http://developer.android.com
• Simplest: download and install Android Studio
bundle (including Android SDK) for your OS
• Alternatives:
– Download/install Android Developer Tools from this
site (based on Eclipse)
– Install Android SDK tools by themselves, then install
ADT for Eclipse separately (from this site)
• We’ll use Android Studio with SDK included
(easy)
5

6. Install!
6

7. Getting Started (3)
• Install Android Studio directly (Windows, Mac); unzip to directory
android-­‐studio, then run ./android-­‐studio/bin/studio.sh (Linux)
• You should see this:
7

8. Getting Started (4)
• Strongly recommend testing
with real Android device
– Android emulator: very slow
– Faster emulator: Genymotion
[14], [15]
– Install USB drivers for your
Android device!
• Bring up the Android SDK
Manager
– Recommended: Install
Android 2.2, 2.3.3 APIs and
4.x API
– Do not worry about Intel x86
Atom, MIPS system images
Settings
Now you’re ready for Android development!
8

9. Outline
• Getting Started
• Android Programming
9

10. Introduction to Android
• Popular mobile device
OS: 52% of U.S.
smartphone market [8]
• Developed by Open
Handset Alliance, led by
Google
• Google claims 900,000
Android device
activations [9]
Source: [8]
10

11. 11

12. Android Highlights (1)
• Android apps execute on
Dalvik VM, a “clean-room”
implementation of JVM
– Dalvik optimized for efficient
execution
– Dalvik: register-based VM,
unlike Oracle’s stack-based
JVM
– Java .class bytecode translated
to Dalvik EXecutable (DEX)
bytecode, which Dalvik
interprets
12

13. Android Highlights (2)
• Android apps written in Java 5
– Actually, a Java dialect (Apache Harmony)
– Everything we’ve learned still holds
• Apps use four main components:
– Activity: A “single screen” that’s visible to user
– Service: Long-running background “part” of app (not
separate process or thread)
– ContentProvider: Manages app data (usually stored in
database) and data access for queries
– BroadcastReceiver: Component that listens for particular
Android system “events”, e.g., “found wireless device”,
and responds accordingly
13

14. App Manifest
• Every Android app must include an
AndroidManifest.xml file describing functionality
• The manifest specifies:
– App’s Activities, Services, etc.
– Permissions requested by app
– Minimum API required
– Hardware features required, e.g., camera with
autofocus
– External libraries to which app is linked, e.g., Google
Maps library
14

15. Activity Lifecycle
• Activity: key building
block of Android apps
• Extend Activity class,
override onCreate(),
onPause(), onResume()
methods
• Dalvik VM can stop any
Activity without warning,
so saving state is important!
• Activities need to be
“responsive”, otherwise
Android shows user “App
Not Responsive” warning:
– Place lengthy operations in
Runnable Threads,
AsyncTasks
Source: [12]
15

16. App Creation Checklist
• If you own an Android device:
– Ensure drivers are installed
– Enable developer options on device under Settings,
specifically USB Debugging
• Android 4.2+: Go to Settings→About phone, press Build number 7
times to enable developer options
• For Android Studio:
– Under File→Settings→Appearance, enable “Show tool
window bars”; the Android view shows LogCat, devices
– Programs should log states via android.util.Log’s
Log.d(APP_TAG_STR,
“debug”), where APP_TAG_STR is a
final String tag denoting your app
– Other commands: Log.e() (error); Log.i() (info); Log.w()
(warning); Log.v() (verbose) – same parameters 16

17. Creating Android App (1)
• Creating Android app
project in Android
Studio:
– Go to File→New Project
– Enter app, project name
– Choose package name
using “reverse URL”
notation, e.g.,
edu.osu.myapp
– Select APIs for app, then
click Next
17

18. Creating Android App (2)
• Determine what kind of
Activity to create; then
click Next
– We’ll choose a Blank
Activity for simplicity
• Enter information about
your Activity, then click
Finish
• This creates a “Hello
World” app
18

19. Deploying the App
• Two choices for deployment:
– Real Android device
– Android virtual device
• Plug in your real device;
otherwise, create an Android
virtual device
• Emulator is slow. Try Intel
accelerated version, or perhaps
http://www.genymotion.com/
• Run the app: press “Run”
button in toolbar
19

20. Underlying Source Code
package
edu.osu.helloandroid;
import
android.os.Bundle;
import
android.app.Activity;
import
android.view.Menu;
public
class
MainActivity
extends
Activity
{
@Override
protected
void
onCreate(Bundle
savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
@Override
public
boolean
onCreateOptionsMenu(Menu
menu)
{
//
Inflate
the
menu;
this
adds
items
to
the
action
bar
if
it
is
present.
getMenuInflater().inflate(R.menu.main,
menu);
return
true;
}
}
src/…/MainActivity.java
20

21. Underlying GUI Code
<RelativeLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context=".MainActivity"
>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/hello_world"
/>
</RelativeLayout>
res/layout/activity_main.xml
– RelativeLayouts are quite complicated. See [13] for details 21

22. The App Manifest
<?xml
version="1.0"
encoding="utf-­‐8"?>
<manifest
xmlns:android="http://schemas.android.com/apk/res/android"
package="edu.osu.helloandroid"
android:versionCode="1"
android:versionName="1.0"
>
<uses-­‐sdk
android:minSdkVersion="8"
android:targetSdkVersion="17"
/>
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme"
>
<activity
android:name="edu.osu.helloandroid.MainActivity"
android:label="@string/app_name"
>
<intent-­‐filter>
<action
android:name="android.intent.action.MAIN"
/>
<category
android:name="android.intent.category.LAUNCHER"
/>
</intent-­‐filter>
</activity>
</application>
</manifest>
AndroidManifest.xml
22

23. A More Interesting App
• We’ll now examine an
app with more features:
WiFi Tester (code on
class website)
• Press a button, scan for
WiFi access points
(APs), display them
23

24. Underlying Source Code (1)
@Override
public
void
onCreate(Bundle
savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_wi_fi);
//
Set
up
WifiManager.
mWifiManager
=
(WifiManager)
getSystemService(Context.WIFI_SERVICE);
//
Create
listener
object
for
Button.
When
Button
is
pressed,
scan
for
//
APs
nearby.
Button
button
=
(Button)
findViewById(R.id.button);
button.setOnClickListener(new
View.OnClickListener()
{
public
void
onClick(View
v)
{
boolean
scanStarted
=
mWifiManager.startScan();
//
If
the
scan
failed,
log
it.
if
(!scanStarted)
Log.e(TAG,
"WiFi
scan
failed...");
}
});
//
Set
up
IntentFilter
for
"WiFi
scan
results
available"
Intent.
mIntentFilter
=
new
IntentFilter();
mIntentFilter.addAction(WifiManager.SCAN_RESULTS_AVAILABLE_ACTION);
}
24

25. Underlying Source Code (2)
• Code much more complex
• First get system WifiManager
• Create listener Object for button that
performs scans
• We register Broadcast Receiver,
mReceiver, to listen for
WifiManager’s “finished scan” system
event (expressed as Intent
WifiManager.SCAN_RESULTS_
AVAILABLE_ACTION)
• Unregister Broadcast Receiver when
leaving Activity
@Override
protected
void
onResume()
{
super.onResume();
registerReceiver(mReceiver,
mIntentFilter);
}
@Override
protected
void
onPause()
{
super.onPause();
unregisterReceiver(mReceiver);
}
25

26. The Broadcast Receiver
private
final
BroadcastReceiver
mReceiver
=
new
BroadcastReceiver()
{
@Override
public
void
onReceive(Context
context,
Intent
intent)
{
String
action
=
intent.getAction();
if
(WifiManager.SCAN_RESULTS_AVAILABLE_ACTION.equals(action))
{
Log.e(TAG,
"Scan
results
available");
List<ScanResult>
scanResults
=
mWifiManager.getScanResults();
mApStr
=
"";
for
(ScanResult
result
:
scanResults)
{
mApStr
=
mApStr
+
result.SSID
+
";
";
mApStr
=
mApStr
+
result.BSSID
+
";
";
mApStr
=
mApStr
+
result.capabilities
+
";
";
mApStr
=
mApStr
+
result.frequency
+
"
MHz;";
mApStr
=
mApStr
+
result.level
+
"
dBmnn";
}
//
Update
UI
to
show
all
this
information.
setTextView(mApStr);
}
}
};
26

27. User Interface
Updating UI in code
private
void
setTextView(String
str)
{
TextView
tv
=
(TextView)
findViewById(R.id.textview);
tv.setMovementMethod(new
ScrollingMovementMethod());
tv.setText(str);
}
• This code simply has the UI display
all collected WiFi APs, makes the
text information scrollable
UI Layout (XML)
<LinearLayout
xmlns:android="http://schemas.android.com/apk/
res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical">
<Button
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:id="@+id/button"
android:text="@string/button_text"/>
<TextView
android:id="@+id/header"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="@string/ap_list"
tools:context=".WiFiActivity"
android:textStyle="bold"
android:gravity="center">
</TextView>
<TextView
android:layout_width="fill_parent"
android:layout_height="fill_parent"
tools:context=".WiFiActivity"
android:id="@+id/textview"
android:scrollbars="vertical">
</TextView>
</LinearLayout>
27

28. Android Programming Notes
• Android apps have multiple points of entry: no main() method
– Cannot “sleep” in Android
– During each entrance, certain Objects may be null
– Defensive programming is very useful to avoid crashes, e.g.,
if
(!(myObj
==
null))
{
//
do
something
}
• Java concurrency techniques are required
– Don’t block the “main” thread in Activities
– Implement long-running tasks such as network connections
asynchronously, e.g., as AsyncTasks
– Recommendation: read [4]; chapter 20 [10]; [11]
• Logging state via android.util.Log throughout app is essential
when debugging (finding root causes)
• Better to have “too many” permissions than too few
– Otherwise, app crashes due to security exceptions!
– Remove “unnecessary” permissions before releasing app to public
• Event handling in Android GUIs entails many listener Objects
28

29. Concurrency: Threads (1)
• Thread: program unit (within process) executing independently
• Basic idea: create class that implements Runnable interface
– Runnable has one method, run(), that contains code to be executed
– Example:
public
class
OurRunnable
implements
Runnable
{
public
void
run()
{
//
run
code
}
}
• Create a Thread object from Runnable and start() Thread, e.g.,
Runnable
r
=
new
OurRunnable();
Thread
t
=
new
Thread(r);
t.start();
• Problem: this is cumbersome unless Thread code is reused
29

30. Concurrency: Threads (2)
• Easier approach: anonymous inner classes, e.g.,
Thread
t
=
new
Thread(new
Runnable(
{
public
void
run()
{
//
code
to
run
}
});
t.start();
• Idiom essential for one-time network connections in
Activities
• However, Threads can be difficult to synchronize,
especially with UI thread in Activity. AsyncTasks are
better suited for this
30

31. Concurrency: AsyncTasks
• AsyncTask encapsulates asynchronous task that interacts with UI thread
in Activity:
public
class
AsyncTask<Params,
Progress,
Result>
{
protected
Result
doInBackground(ParamType
param)
{
//
code
to
run
in
background
publishProgress(ProgressType
progress);
//
UI
…
return
Result;
}
protected
void
onProgressUpdate(ProgressType
progress)
{
//
invoke
method
in
Activity
to
update
UI
}
}
• Extend AsyncTask with your own class
• Documentation at http://developer.android.com
31

32. Thank You
Any questions?
32

33. References (1)
1. C. Horstmann, Big Java Late Objects, Wiley, 2012. Online: http://proquest.safaribooksonline.
com.proxy.lib.ohio–state.edu/book/–/9781118087886
2. J. Bloch, Effective Java, 2nd ed., Addison–Wesley, 2008. Online: http://proquest.
safaribooksonline.com.proxy.lib.ohio–state.edu/book/programming/java/9780137150021
3. S.B. Zakhour, S. Kannan, and R. Gallardo, The Java® Tutorial: A Short Course on the Basics,
5th ed., Addison–Wesley, 2013. Online: http://proquest.safaribooksonline.com.proxy.lib.
ohio–state.edu/book/programming/java/9780132761987
4. C. Collins, M. Galpin, and M. Kaeppler, Android in Practice, Manning, 2011. Online:
http://proquest.safaribooksonline.com.proxy.lib.ohio–state.edu/book/programming/android/
9781935182924
5. M.L. Sichitiu, 2011, http://www.ece.ncsu.edu/wireless/MadeInWALAN/AndroidTutorial/PPTs/
javaReview.ppt
6. Oracle, http://docs.oracle.com/javase/1.5.0/docs/api/index.html
7. Wikipedia, https://en.wikipedia.org/wiki/Vehicle_Identification_Number
8. Nielsen Co., “Smartphone Milestone: Half of Mobile Subscribers Ages 55+ Own
Smartphones”, 22 Apr. 2014, http://www.nielsen.com/us/en/insights/news/2014/
smartphone-milestone-half-of-americans-ages-55-own-smartphones.html
9. Android Open Source Project, http://www.android.com
33

34. References (2)
10. http://bcs.wiley.com/he-bcs/Books?action=index&itemId=1118087887&bcsId=7006
11. B. Goetz, T. Peierls, J. Bloch, J. Bowbeer, D. Holmes, and D. Lea, Java Concurrency in
Practice, Addison-Wesley, 2006, online at
http://proquest.safaribooksonline.com/book/programming/java/0321349601
12. https://developer.android.com/guide/components/activities.html
13. https://developer.android.com/guide/topics/ui/declaring-layout.html#CommonLayouts
14. https://cloud.genymotion.com/page/doc/#collapse4
15. http://blog.zeezonline.com/2013/11/install-google-play-on-genymotion-2-0/
34